Using a vintage stereo amp (L & R only) to play various CDs. Some CDs say Dolby Digital or whatever, some say nothing about stereo or surround. Some passages are very weak compared to all the others. I suspect some of those passages may where most of the sound is in surround channels. Once I read that surround sound can be recovered from a stereo amp by connecting a third speaker between L+ and R- terminals or some such arrangement. Is this correct, or should it be between R+ and L+ or something else? I am retired, do not plan to replace this receiver until it no longer amplifies CDs. Any helpful idea from someone who has solved a similar problem would be greatly appreciated.